Considering first and principally the illustrative and important field of electron beam accelerators, the art has been properly vitally concerned with providing practical and affordable shielding safety in diverse production line and other environments where electron-beam irradiation is to be employed. One of the major barriers to the widespread industrial use of energetic electrons (energies&gt;20 keV in such applications, for example) as for the completion of polymerization in free radical cured systems, for the cross-linking or degradation of various natural and synthetic polymers, and/or for the surface and bulk sterilization of materials, indeed, has been the difficulty residing in the safe introduction of the product to the electron processor or irradiator in a continuous manner, usually at high production-line speeds (e.g. from 30 m/minute to 500 m/minute).
This problem arises from the nature of the energy source. When energetic electrons ultimately stop in material, the relatively unpenetrating particle (electron), as it slows down, dissipates some of its energy in the form of penetrating photons (bremsstrahlung), and causes the excitation of characteristic X-rays from the atoms of the material with which it interacts. The resultant source of penetrating X-ray or photon radiation is difficult to confine due to its great penetrability in solid matter. As a consequence, on-line continuous application of electron curing has been difficult and in some cases has seemed impracticable. Processes which have been developed for wire and cable, polyethylene crosslinking and surface coating curing applications, have been accomplished with vault or volume shielding of the entire system--an approach quite incompatible with most high-speed line-curing requirements.
A breakthrough in successful practical shielding in some industrial applications of electron beam irradiation is described in U.S. Pat. Nos. 4,252,413 and 4,642,244 of the assignee of the present invention; wherein irradiation zones are protected by in-line longitudinally extending housings that, though receiving and passing the surfaces such as webs and other materials, trap the dangerous radiation and side effects to insure safety on the line. An example of the use of such apparatus is the Energy Sciences "Selfshield" type CB/175/105/760 electron beam processor.
The shielding housing also has provision for receiving inert gases, such as nitrogen, in the irradiation zone where the surface-to-be-irradiated is passed by the electron beam accelerator window. For assembly, adjustment and maintenance, the lower half of the longitudinally extending in-line housing is generally moved or opened downward to permit access to the irradiation zone and surface or web or product feed systems.
If the accelerator and its window are not oriented horizontally, but are displaced at an acute angle, the lower half of the longitudinally extending shielding-housing is moved away longitudinally and downwardly for access.
Similarly, where drum type irradiation curing systems are used, as for example, in U.S. Pat. No. 4,521,445 of said assignee, the drum may be incorporated as part of the longitudinally extending shielding housing, again with its lower section downwardly movable to give access to the irradiation and product feedthrough zone.
It has now been discovered, however, that considerable space can be saved and far better and more convenient access to the irradiation and surface feed zones attained, as well as improved shielding efficacy and at lower cost, through a rather radical change of shielding housing design, wherein the construction is transverse or lateral to the sheet material or other surface handling line, and the shielding housing is formed to provide a novel transverse or lateral sliding separation of housing halves, to open and close the irradiation and feed zones.